Repeater-circuits



Q S. DEMAREST AND S. P. SHACKLETUM H'EPEATER CIRCUITS.

APPLICATION FILED MAYH. 1919.

1 382 310 mum J6 28,1921.

2 SHEETS SHEET i- ATTORNEY UNITED STATES PATENT OFFICE.

' "CHARLES s. nEnAREsr, or BROOKLYN, AND SAMUEL r. SHACKLET'ON, on NEWYORK, 'n. Y., 'Assronons r AMERICAN TELEPHONE AND TELEGRAPH COM- rm, ACORPORATION or NEW YORK. I

Specification of Letters Patent.

REPEATER-CIRGUITS.

Patented June 28, 1921.

Application filed May 17, 1919. Serial 1 10. 297,902;

x T 0 all whom it may concern:

, Be it known that we, CHARLES S.DE1\IAREST and SAMUEL P. SHACKLETON,residing at Brooklyn and New York, in the counties of Kings and Bronxand State of New York, respectivel have invented certain Improvements inT?epeater-Circuits, of which the following is a specification.

This invention relates to transmission circuits and more particularly totransmission circuits in which repeatersare employed.

One of the objects of this invention is to simplify the apparatus andreduce the expense connected with the installation of repeater equipmentfor telephone lines. Another object of the invention has reference tothe provision of means whereby one repeater may be employed for aplurality of connecting circuits. Other and further ob jects of theinvention will more fully appear in connection with the detaileddescription hereinafter given. I

Where cord circuit repeaters are employed in the establishing ofconnections between long distance transmission lines, it is customary toprovide a repeater unit for each repeater cord at each position. Undercertain circumstances, however, it is desirable that the same operatingunit be used for repeater cords at two positions so that the. amount ofapparatus necessary may be reduced. The repeater unit comprising theamplifiers, relays, coils, etc., is usually arranged at a point somedistance from the switchboard and is connected with the switching cordsand controlling keys such as the listening, splitting and repeatercontrol keys by means of a series of conductors extending from therepeater unit to the switchboard position. These conductors are of twokinds, those used for transmission purposes and extending to theplugs orother switch ing arrangements of the cords, and those used merely forcontrol or supervisory purposes, and leading to the several controllingkeys. In accordance with the present invention the apparatus is soarranged that the controlling conductors leading from the repeaterunit'may be switched into connection with conductors leading, to thecontrolling keys at either of two switchboard positions. Thetransmission conductors leading to the plugsor other switching meansat-the switchboard positions are connected in parallel to the twopositions. Means are switching plugs at both positions. By thisarrangement of the apparatus the operator who first establishes aconnection has complete control over the repeater and while it ispossible for the operator at the other position to attempt to set up aconnection, substantially no harm can result therefrom since theoperator cannot by means of the controlling keys interfere with theconnec tion already established and cannot by means of her listening setobtain access to the connection which she attempted to es tablish. Theassociation of additional lines with the lines already connected doesnot result in unbalancing the repeater and caus: ing singing for thereason that artificial lines are associated with the circuit at the sametime. In order, however, to prevent the possibility of an operatorattempting to set up an additional connection of this char? acter a busylamp is caused to glow at the other switchboard position when the firstconnection is established in order to indicate that the repeater isalready in use.

The invention may now be more fully un derstood by reference to thefollowing description when read in connection with the accompanyingdrawings, Figures 1 and 2 of which constitute a circuit diagram of oneembodiment of the invention.

Referring to the drawing, a repeater organization of the well knowntwo-way two repeater type including amplifiers A and-A is illustrated.This repeater be associated with either of two switchboard positionsdesignatedas X and Y upon the drawing. In order to interconnect tolllines through the repeater, the operator at posie tion X is providedwith cords terminating in twin plugs P, and 1?, adapted to cooperatewith twin jacks of toll lines. In a similar manner the operator atposition Y is provided with cords terminating in plugs P, and P In orderthat the repeater shown in Fig. 2 may be used in establishingconnections at either switchboard position, the incoming line conductorsL and the corresponding artificial line conductors N of the repeater areconnected in parallel over conductors L and L and conductors N and N tothe incoming twin plugs P and P at the two positions. In a similarmanner-the outgoing conductors L and N are connected in parallel overconductors L and L and over conductors N and N to the out oing twinplugs P and P ormally the repeater is not included in circuit with theincoming and outgoing conducto'rs leading to the switching plugs ateither position to the inconiing' line. Gonductors L are connected tothefline conductors L through a direct connection including conduc'torsCand The conductors and C nia'y ibe interconnected either throughconductors C C and the contaetsof the Splitting key K at position Xorithrough conductors Ci and G and the ont'actsof the splitting'key K atposition In order to exercise control over the connec'tions which may be"established at position Xthroughthe rpeaterfthe operatoratthatjgiosition is provided with a listening key anda repeater controlkey K 1n ad'- ditinnfto the splitting "key K already freferret'i to. Ina simila'r'manner'the operator at position Y is provided with'lis'teningkey 'Ki and repeater control key K in addition to thesplitting 'lrey K The various control circuits which will be hereinafterdescribed as "eirtending from the repeater to the several 'keys at'eachoperators position are arranged to pass over the contacts of a seriesofswitching relays 1,2 and '3. Norinally the cdrd circuit conductors "Cand C aswellas the control circuit conductors are extended 'over theback contacts of these switching relays to the keys K K and K atposition When the switching relays are energized howeverjthe cordcircuit connections as well as the controlling circuitconnectionsiare'shifted from the keys at .po- "sition 'X to thecorresponding 'keysat position Y. I v

In order to effect the switching 'of these circuits by means of theswitching 'rela'ysa double wound relay 4 is provided in thesleeveicirciiitsof the plugs 'P and'P at position Y so that when" eitherorboth o'f'these plugs are inserted in line jacks therelay 4 will beenergized to efi'ectthe shifting of the connections. A similarrelay 5 isprovided in the sleeve circuits of the plugs P and P at position X. Thecircuit of the relay 5 is rendered inoperative when the relay 4 isenergized. In a similar manner when the relay 5. is energized byinserting either or both of plugs P and P in line jacks, the circuit ofthe relay 4 is rendered inoperative so that the switching relays 1 to 3inclusive will remain in their normal condition with the cord conductorsand controlling circuits switched to position X.

The transmission connections extending from the repeater 'to the lineand artificial line contactsof the plugs at "the two positions inparallel are at no time affected by the transfer of the circuit controlfrom one position to the other. This avoids transmission losses whichmight result from the additional relay contacts which would have 'to beprovided in these transmission connections if they were to be shiftedfrom one position to the other.

In order to prevent any possibility o'fc'onfusion arising from oneoperator "at one posiition attempting to set up a connect-ion when therepeater is already em loyed a connectionset up at the other position,busy IampsG and 7 are provided forthe two positions so that whenaconnection is established at one position the busy lamp at the otherposition will be caused to glowfindicating to the operator at thatposition that the apparatus is already in use.

Should the operator a't-o'ne position ignore the busy lamp and insertthe plugs in the jacks of'toll lines, no harm would result so f'ar'asthe repeater iscon'c'erned even though the two connections were crossedsince the operator upon insertin the'twih plug'in the jack connects-asuitable balancing network to the repeater at the same time that thetoll line is connected to the repeater consequently even though twolinesbe connected in parallel 'to "each end of the repeater, *therepeater will still remain balanced andsinging will'not'result. 7

By placing the controlling circuits under the control of the operatorwhofirst established the connection, the second operator will beunabletointerfere with-thecon'ne'c tion established by the first o eratorsymanipulating any o'f her controlling keys and Assuming that theoperatorat-position desires to setup connection "betw'een two to'lllineslthro'ugh the repeater shown in Fig.2, the plug P will 'be insertedin the j'ackj of the incoming line thereby completing a'circuit from thegrounded sleeve contacts "of said jack over "sleeve contactsof the plugP through the left handwinding ofrel'aiy 5 and over theright'handback'contact ofr'elay 4 to battery.Aparallelcircuit'isestablished at the same timeoverthe groun'deli sleevecontacts of the jack, sleeve contacts of the plug P inner left hand backcontact of relay 4 and over conductor 8 through the winding of relay 9to battery.

Relay 5 upon being energized disconnects battery at its left handcontact from the windings of relay 4 thereby preventing the energizationof said relay due to the operator at station -Y attempting to establisha connection through the plugs P and P Relay 5 at its left hand frontcontact completes a circuit from battery over conductor 10 and throughthe busy'lamp .7 to ground thereby causing the lamp to glow to indicateto the o erator at position Y that the repeater is a ready in service.Relay 5 by opening its right hand contacts disconnects the sleeveconductors of plugs P and P, from the sleeve relays 9 and 12. Theswitching relays 1, 2 and 3 are under the control of the relay 4 and asthis relay has been rendered inoperative by the relay 5 the switchingrelays cannot be affected by any attempt of the operator at position Yto set up a connection.

Returning to relay 9 whose circuit was completed by inserting the plug Pin the line jack, the energization of said relay results in thecompletion of a circuit from ground over the lower front contact of saidrelay to point 13 from which point the circuit extends over conductors14 and 15,back contacts of ringing responsive relays 16 and 17 in seriesand over conductor 18 through the winding of relay 19 to battery. Relay19 is energized over the circuit above described and by opening itsright hand contact prevents the energization of relay 20 which wouldotherwise result from the connection of ground to the point 13.

A direct connection now extends between the line contacts of plugs P andP over conductors L and 11, back contacts of relay 21, conductors C,back contacts of relay 3, conductors C normal right hand contacts ofsplitting key K conductors 22, normal left hand contacts of splittingkey K conductors C back contacts of relay 2, conductors C, back contactsof relay 23 and over conductors L and L to plug P The operator byactuating the listening key K, may bridgeher set across the transmissionpath above traced at points 24 and 25.

In order to complete the connection to the outgoing transmission line,the operator may insert the plug P in the jack of the outgoingtransmission line and operate the repeater control key K,. A circuit iscompleted from the grounded sleeve contacts of the outgoing line iackover the sleeve contacts of the plug P through the right hand winding ofrelay 5 and over the right hand contact of relay 4 to battery. Thiscircuit is without effect as relay 5 had already been energized throughits left hand winding. A parallel circuit is completed over the sleevecontacts of plug]? over the left hand contact of relay 4 and through thewinding of relay 12 to battery. Relay 12 is therefore energized andatits lower contact connects ground to point 13 in par allel with theground connected over the contact of relay 9. The actuation of the repeater control key K completes a circuit for the filament control relay29 from battery through the winding of said relay over conductor 30,right hand back contact of relay 3 over conductor 31, right hand makecontact of key K over conductors 32, 3 3 and 14 to point 13 and thenceto. ground over the lower front contacts of relays 9 and 12. Theenergization of relay 29 over the circuit above traced results in thecompletion of the filament circuit from battery B through the filamentsof the amplifiers A and A rendering the tubes operative.

The actuation of the repeater control key K also results in completing acircuit from grounded point 13, over conductor 34, right hand backcontact of relay 1, conductors 35 and 36, also normal right hand andleft hand contacts of splitting key K ri ht hand normal contact oflistening key k conductor 37, inner left hand back contact of relay 1,conductor 38,-upper front contacts of relays 9 and 12,'conductors 39 and40, left'hand make contact of key K conductors 41, 42 and 43 through thewinding of relay 44, back contact of relay 45 over conductor 46 andthence in parallel through the windings or relays 21 and 23 to battery.Relays 44, 21 and 23 are energized over the circuit above traced, theformer operating to open the short circuit normally existing about theprimaries of input transformers 47 and 48 of the repeater and to connectsaid transformers to input bridges 49 and 50 of the repeater. Relays 21and 23 operate to disconnect the line conductors L and L from the cordconductors U and C and to connect the repeater in circuit.

With the circuit in the condition just described, transmission from theincoming line passes over conductors L and L over the front contacts ofrelay 21, through the input bridge 49 and input transformer 47 throughthe amplifier A, where the variations are amplified, to the outputcircuit 53 and transformer 52. At the transformer the energy divides,part flowing to the outgoing line over the front contacts of relay 23and conductors L and L and part flowing to the artificial line overconductors N and N In a similar manner transmission from the outgoingline passes over conductors L and L over the front contacts ofrelay 23to the input bridge 50 and input transformer 48 through the amplifier Ato the output circuit 54 and output transformer 51 where the energydivides, part flowing over the front contacts of relay 21 and conductorsL anclL to the incoming line and part flowing over conductors N and N tothe artificial line. I

If, with the circuit in this condition, ringing current should betransmitted from the incoming line, the ringing current will flowover'conductors L and L to ringin responsive relay 17 which will beactuate to open the circuit previously traced through relay 19. Relay 19is accordingly deenergized and completes a circuit from:gr-oundedfipoint 13 over the back contact of relay 19 and through theWinding of relay 20 to battery. Relay'20 at its right hand'front contactcompletes a circuit for relay '45 which-may be traced from groundedpoint -13'over conductor 34, right hand back contact of relay 1,conductors 35 an'd36 lower normal contacts of the splitting key k righthand normal contactof listenin key K conductor 37, inner left hand baccontact-' of relay 1, conductor'38, upper front contacts of relays 9and12, conductors 39- and 40, left hand make contact of key K conductors4'1, 42 and 55, front right hand contact of relay20 and through thewinding of relay 45 to battery. Relay 45 upon being energized opens thecircuit previously traced through relays 44, 21 and 23 and atits-frontcontact com'pletes a holding circuit for relays 21 and 23 from groundover conductor-46 and through the windings of said relays to battery.Relay 44 is deenergized and again short circuits the input windings ofthe transformers 47 and 48 to prevent ringingcurrent from beingtransmitted to the repeater.

Returning to relay 20, saidrelay at its left hand front contactcompletes a circuit from grounded point;13 over the left hand frontcontact of relay 20 through the winding of relay '56 to battery. Relay'56 completes a locking circuit over its upper frontcontact overconductors 57 and 58, left hand normal contact of key K conductors 59and 35, right hand back contact of relay 1 to grounded point 13. At itslower front contact relay 56 completes a circuit'fromg'round overconductor 60, left hand back contact of relay 1 and through the lamp 61tobattery. The lamp '61 now glows to indicate tothe operator that a ringhas'come in from one of the toll line's.

The operator may now actuate the listenink key K which, by opening'itsleft hand contact, breaks the locking circuit of relay 56 with theconsequent eifacement of the lamp 61. Key K by openingits right handcontact breaks the circuit previously traced to relay 45 which isdeenergizedand again connects relay 44 in circuit with relays 21 and 23.The original circuitof theserelays, however, it will be remembered,passes over the right hand contact of the'key K so that relays 21 and23-are now denergized in addition to the relay 44. 'Thedeenergization ofrelays21 and 23-resultsin again interconnectingtheline conductors L'andLthrough the cord connection includingconductors C, 0, the splittingkey Kand cOnd'uctOrS C and 0 .1 The'operators set is now. bridged across thiscircuit and the operator upon ascertaining that the iCELll came in fromthe incoming line may, ifishe desires, :throw, the splitting key K tothe leftvthereby (llSCOII-r necting the outgoing end of thegc'ircuit sothat her set will remainconnected 'tothe incoming line to the exclusionof the outgoing line. p

If, with the circuit in the condition just described, ringing currentshould be trans? mitted over the outgoing line, the tI'ELIISmlt-I tedringingcurrent wouldjpass over conductors L and. L to theringing-responsive relay 16 thereby again opening the circuit of therelay 19 which was, "of course,restored as-soon as relays? ceased torespond to ringing current. elay 19-again closes thecircuit of-relay 2Owhicha ain completes the circuit of relay :56 but 1 oes not cause theenergization of relay 45 gas the circuit of the latter relay is heldopen at the -con-. tacts of the listening and splitting keys. A lockingcircuit 'forrelay-56 is completed over the upper front contact ofsaidrelay over conductors 57, 58 and 62, lower left hand make contact 1 ofsplitting key K lower right hand normal contact of said key overconductors 36 and 35, right hand back contact of relay 1 and-overconductor 34 to grounded point 13. Relay56 again completes -the'cir cuitof the lamp 61 whereuponthe operator is informed that a call has come inover the outgoing line.

The operator maythen throw the splitting key to the right therebydisconnecting the incoming line from the circuitandleaving her setbridged across the outgoing line. The actuation of the Splitting keymomentarily opens the locking circuit above traced for relay 56 which isaccordingl deene'rgized and effaces the lamp 61. S ould the operatorrestore the listening key K and the splitting key K to normal, thecircuit originally traced for relays 44, 21 and 23 would be againcompleted so that the re-' peater is again rendered, operative and isconnected in the transmission circuit.

Should the operator desire to take down the connection she will withdrawplugs P and R from the line jacks and restore the key K. to normal. Thewithdrawal of the plugs P and P breaks the circuits through bothwindings of relay 5 and through the relays 9 and 12 so that these relaysare restored to normal. The lamp 7 is effaced bythe deenergization ofrelay 5 and battery is again connected to the windings of relay 4.. Thedeenergization of relays 9 and 12 removes the ground connection frompoint 13 so that relays 19, 29, 44, 21 and 23 are deenergized it beingremembered that the circuits of all of these relays pass to groundthrough point 13. The apparatus is now in a normal condition and readyfor the completlon of a connection at either position X or position Y.

It will be noticed with reference to the connection described as havingbeen set up at the osition X, that the various circuits control ed bykeys K K and K extended from the repeater to said keys over the backcontacts of switching relays 1, 2, and 3. Alternative connections areprovided to the keys K K and K, at position Y but these connections areinoperative since they are maintained open at the contact of theswitching relays, 1, 2 and 3. The operator at position Y is thereforeunable to control the repeater or in any way change the condition of theconnection established at position X by manipulating her controllingkeys. Should the operator at position Y fail to observe the busy lamp 7and insert either or both of the plugs P, and P in the jacks of tolllines, the toll lines in question will be connected in parallel with thetoll lines interconnected through the repeater at position X. However,at the same time suitable balancing artificial lines are connected inparallel to the artificial lines involved in the connection at station Xso that the repeater is not unbalanced and therefore does not sing. Theoperator at position Y is unable, by throwing her listening key, tobridge her set across the connection and will therefore realize that therepeater is in use and will withdraw the plugs inserted in the toll linejacks.

With the apparatus restored to normal as above described, the operatorat position Y may establish a connection through the repeater at Fig. 2by employing the plugs P and R The insertion of the plug P, in the jackof the incoming line completes a circuit over the sleeve contacts of theplug through the left hand winding of relay 4 to battery. A circuit isalso'completed over the sleeve contacts of the plug and over the innerright hand contact of relay 5 and over conductor 8 through the windingof relay 9 to battery. Relay 4 at its right hand contact disconnectsbattery from the windings of the relay 5 thereby rendering the latterinoperative and at its right hand front contact relay 4 completes acircuit from battery to the busy lamp 6 to indicate to the operator atposition X that the repeater is in use. By opening its left handcontacts, relay 4 disconnects relays 9 and 12 from the sleeve conductorsof plugs P and P Relay 4 at its right hand front contacts also completesa circuit from battery over conductor 63 and through the windings ofrelays 1., 2 and 3 in parallel to ground. These Relay 9 at its lowerfront contact upon being energized completes the previously tracedcircuit of the relay 19 which holds open the circuit of the relay 20.Atransr mission connection now exists from the incoming line over theleft hand tip and ring 7 contacts of the plug P, over conductors L andL, back contacts of relay 21, conductors C, front contacts of relay 3,conductors C,, over the normal contacts of splitting key K overconductors G front 30 contacts of relay 2, conductors C, back contactsof relay 23 and over conductors L and L to the right hand tip and ringcontacts of plug P The operator by throwing listening key K, may bridgeher set across the transmission clrcuit above traced.

In order to complete the connection, the operator will insert the plug Pin the jack of the outgoing line and throw the repeater control key Kthe listening key K, being restored to normal. A circuit is completedover the sleeve conductor of the plug P through the right hand windingof relay 4 and over the back left hand contact of relay 5 to battery butas relay 4 is already energized this circuit is without effect. A circuit is also completed over the sleeve conductor of the plug P and overthe right hand back contact of relay 5, over conductor 11 and to thewinding of relay 12 to battery.

Relay 12 at its lower contact now connects ground to point 13 inparallel with the ground applied to said point over the lower contact ofrelay 9.

A circuit for the filament control relay 29 is completed from batterythrough the winding of said relay over conductor 30, right hand frontcontact of relay 3, conductor 31, right hand make contact of key K, overconductors 32, 33 and 14to grounded point 13. A circuit is alsocompleted for relays 44,21 and 23 from grounded point 13 over conduc tor34, front right hand contact of relay 1, conductors 35' and 36, over thelower normal contacts of key K over the right handJlS normal contact oflistening key K over conductor 37 inner left hand front contact of relay1, conductor 38, upper front contacts of relays 9 and 12, conductors 39and 40, left hand make contact of key K conductors 41', 42 and43'through the winding of relay 44 over the back contact of relay 45,over conductor 46, through the windings of relays 21 and 23 to battery.The energization of relays 29, 44, 21 and 23 results in the same certainchanges as already described with reference to the connectionestablished at position X.

With the circuit in this condition, transmission from the iQQQIDiI gline passes over 20 in: a manner already described.

conductors L and L, over the front contacts-of relay 21 through inputbridge 49, transformer 47 and amplifier A to output circuit 53 andoutgoing transformer 52 where 1 thegenergy divides, part beingtransmitted over the front contacts of relay 23 and conductors L and Lto the outgoing line and part being transmitted over conductors N and Nto the artificial line. In a similar manner transmission incoming fromthe outgoing lines passes over conductors L L and the: front' contactsof relay 23 through input bridge 50 and transformer 48 and throughamplifier A of the repeater to the outgoing transformer 51 Where'theenergy divides, part being transmitted over the front contacts of relay21 and conductors L and L to the incoming line and part beingtransmitted over conductorsv N and N to the corresponding artificialline.

Should ringing current be transmitted over the incoming line the relay1'? will be energized to open the circuit of relay 19 which, in turn,completesthe circuit of relay Relay 20 at its right hand front contactcompletes the circuit of relay 45 over a path extending from groundedpoint 13 overconductor 34, right hand. front contact of relay 1,conductors- 35 and 36, lower normal contacts of the splitting key Kright hand normal contact of listening key toconductor 37, inner lefthand front contact of relay 1 conductor 38, upper front: contacts ofrelays 9 and 12, conductors 39 and 40, left hand make contact of key Kconductors 41, 42'

and 55 over the right hand front contact. of relay 20 and through thewindings of relay 45 to battery. The energization'of relay 45 producescircuit changes similar to those already described with reference to the0011- nection set up at position X.

Relay 20 at its left hand front contact completes the circuit of relay56 which is locked up over-a circuit extending over its upperfrontcontact over conductors 5'7 and 58 over the left hand normalcontact of key K over conductors 59 and 35, right hand front contact ofrelay 1 and over con.- ductor 34 to grounded point 13. At its lowerfront contact relay 56 completes a eircuit from ground over conductor60, left hand front contact of relay 1 and through the lamp 61 tobattery. The glowing ,of lamp 61" indicates to the operator that a ringhas been transmitted over one of the connected lines. The operator maythenactuate her listening key which causes the deenergization of relay56 thereby efi'acing the lamp 61. The actuation of the listening keyalso opens the circuit of relay 45 and causes a den'ergization ofrelays'21 and 23 inaddition to relay 44. The two toll lines are. nowdirectly interconnected through the cord- 'circuit connections includingconductors C, C

ing current was transmitted from the out-, I

going line, ringing responsive relay 16 would be actuated to againrestore the slow release relay 19 which in turncompletes the circuit ofrelay 20; The energization of relay 20 does: not complete the circuit ofrclay 45 as the circu it of said relayv is heldopcn at the contacts ofthekeys K and K The circuit of relay 56, however, is corn-. pleted atthe left hand front contact of relay 20 and relay 56 at its upper frontcontact establishes a locking circuit over conductors 57. 58 and 62",over the lower left hand make contact of'splitting key K over the lowerright hand normal contact of said key, over conductors 3:6 and 3-5;right hand front contact of relay 1 and over conductor 34 to groundedpoint 13. Relay 56- com pletes the circuit of the lamp 61 therebyindicating to the operator that, a'ring has come in from the outgoingline. The operator may then throw the splitting key to the right inorder to communicate over the outgoing line to the exclusion of theincoming line.- The operation momentarily opens the look ing circuit'ofrelay 56 which is deenergized and eff'aces the lamp 61.

As soon as the operator restores the listening and splitting keys, K andK respectively, the circuit of relays 44, 21 and 23 is again completedso that the repeater is once more rendered operative and is againconnected in the transmission circuit previously described. Theconnection may be taken down by withdrawing plugs P and P and restoringthe repeater control key K Relays 4, 9 and 12 are deenergized upon withdrawing the plugs. e Thevcl'eenergization of relay 4 restores switchingrelays 1, 2 and? to normal and the dei-Snergization ofrelays 9 and 12 bydisconnecting ground from point 13 restores relays 19 2.9., 44', 21 and23. to normal. e

It'will be observed that-under the conditions-just describedtheconnections from the repeater to the controlling keys K' f, K and- K atposition Y were wholly under the control of the operator at saidpositionand the corresponding connections to the keys. at position X were heldopen so: that the operator at the latter position was unable to controlthe repeater'or in any manner affect the connection established atposition Y. Should the operator at position X disregard the busy lampand attempt toconnect to a transmission line, she would, therefore beunable to listen in on the line and even though the line be connected inparallel with a line involved in the connection established at positionY, the repeater would not be unbalanced for the reason that acorresponding artificial line would be connected in the circuit at thesame time.

By means of the arrangement above described, the same repeater may beused for establishing connections at two positions thereby eliminating acertain amount of apparatus with a consequent reduction in the expenseinvolved in the installation.

It will also be observed that the general principles herein disclosedmay be embodied in many other organizations widely diflerent from thatillustrated without departing from the spirit of the invention asdefined in the following claims.

What is claimed is:

1. In a signaling system, a repeater, a plurality of lines, a pluralityof sets of switching apparatus for associating the repeater with a line,parallel transmission connections extending from said repeater to eachset of switching apparatus, keys associated with each set of switchingapparatus for controlling the functioning of the repeater, and meanswhereby when the repeater is associated with a line by one set ofswitching apparatus the repeater will be rendered independent of thecontrolling keys of another set of switching apparatus withoutdisturbing said parallel transmission connections.

2. In a signaling system, a repeater, a plurality of switch boardpositions, lines terminating at said positions, parallel transmissionconnections extending from said repeater to each position over whichsaid repeater may be associated with lines at that position, controllingkeys at each position, connections whereby the control of the repeatercan be extended to the keys at any one of the positions, and meanswhereby when the repeater is associated with a line at one position theconnections from the repeater to the corresponding controlling keys willbe established and the repeater rendered independent of othercontrolling keys without disturbing said parallel transmissionconnections.

3. In a signaling system, a repeater, a plurality of switch boardpositions, lines terminating at said position in jacks, cords at eachposition terminating in plugs adapted to cooperate with said jacks,parallel transmission connections extending from the repeater to theplugs at different positions, controlling keys at each position,connections whereby the control of the repeater may be extended to thecontrolling keys at any one of the positions, and means responsive tothe insertion of the plugs at one position in the jack of a line at thatposition to establish a connection from the repeater to the controllingkeys at that position and render the repeater independent of keys atanother position without disturbing the parallel transmissionconnections to other plugs.

4. In a signaling system, a repeater, a plurality of switch boardpositions, lines terminating at said positions in jacks, cords at eachposition terminating in plugs adapted to cooperate with said jacks,parallel transmission connections extending from the repeater to theplugs at diilerent positions, controlling keys at each position,connections normally extending from the repeater to the controlling keysat one position, and means whereby when a plug at another position isinserted in the jack of a line at that position the repeater isdisconnected from the keys at the first position and connected to thekeys at the second position without disturbing the parallel transmissionconnections of other plugs.

5. In a signaling system, a repeater, a plurality of lines, a pluralityof sets of switching apparatus for associating the repeater with a line,parallel transmission connections extending from said repeater to eachset of switching apparatus, keys associated with each set of switchingapparatus for controlling the functioning of the repeater, busy signalsassociated with each set of switching apparatus, and means whereby whenthe repeater is associated with a line by one set of switching apparatusthe repeater will be rendered independent of the controlling keys ofanother set of switching apparatus without disturbing said paralleltransmission connections, and whereby a busy signal associated with saidother set of switching apparatus will be operated.

6. In a signaling system, a repeater, a plurality of switch boardpositions, lines terminating at said positions, parallel transmissionconnections extending from said repeater to each position over whichsaid repeater may be associated with lines at that position, controllingkeys at each position, connections whereby the control of the repeatercan be extended to the keys at any one of the positions, busy signals ateach position, and means whereby when the repeater is associated with aline at one position the connections from the repeater to thecorresponding controlling keys will be established and the repeaterrendered independent of other controlling keys without disturbing saidparallel transmission connections, and whereby a busy signal at anotherposition will be operated.

In testimony whereof, we have signed our names to this specificationthis 16th day of May, 1919.

CHARLES S. DEMAREST. SAMUEL P, SHACKLETON.

